1. Field of the Invention
This invention generally relates to wireless local area network (wLAN) communications and, more particularly, to an admission system and method for quality of service (QoS) communications in IEEE 802.11e and IEEE 802.11 networks.
2. Description of the Related Art
For devices operating in a network that supports QoS and managed bandwidths, there is a need for an entity that provides admission control, and the reallocation of bandwidth to the admitted data streams, as needs change. Such as entity would also enforce any existing allocations. Further, the entity would ideally monitor the channel, to ensure that the streams' actual usage of bandwidth matched the requested (assigned) amount of bandwidth. All these functions would fall under the responsibility of a network bandwidth manager (BM).
In order for the bandwidth to be managed, several mechanisms and objects are needed. Each device needs to have an entity that sends the required messaging to the BM. The BM, in turn, resides in the device that contains the hybrid coordinator (HC). To avoid confusion, this device entity is referred to herein as a controller. Further, there is a need for a protocol that specifies messaging, and the processes for reserving bandwidth. The IEEE 802.11e Draft D2.0 includes one example of such messaging. RSVP (Resource ReSerVation Protocol) is another such example. RSVP is a Layer 3 protocol that may be used by Internet Protocol (IP) traffic. The controller, hence, should have the ability to support protocols at both Layer 2 as well as Layer 3.
The suggested protocols address the administration of bandwidth admission and control using a token bucket system. For example, in the IP world, it is very common to define bandwidth as a number of bytes per second. The mechanism that is used is based on a token bucket wherein each user is allowed to transmit up to rT+b bytes, in T seconds, where r and b are the mean data rate in bytes per second and maximum burst size in bytes, respectively, that have been requested/assigned to the stream. However, the token bucket mechanism is appropriate only in the case where there are multiple queues at the same node, as in a router.
Local area networks (LANs) typically use a Carrier Sense Multiple Access (CSMA) scheme, in order to support parameterized QoS. To support packet transmission meeting requirements for throughput, latency and jitter, the system must be able to allocate time on the channel in such a way that coexistence with CSMA-based transmissions is not greatly affected. Moreover, packet error rates in such systems are typically large if the medium is wireless or power-line based, typically greater than 10%.
Several solutions have been proposed to solve the problem of packet transport meeting parameterized QoS objectives. However, these proposals have been found lacking in one or more aspects. The original drafts of 802.11e included an object called a TSPEC (for Transmission Specification), but no means were provided for specifying an upper bound on channel occupancy required for admission in a given stream. Nor was any means provided for objectively verifying that a request for the transport of packets meeting specific QoS objectives could be met.
In addition, this type of TSPEC is blind to the fact that the channel makes errors, and therefore, an over-reservation of bandwidth is generally required. Moreover, this type of TSPEC cannot be used with power saving devices, since there is no guarantee of time when a sequence of packets wouldn't be delivered.
Time-based polling techniques have previously been considered. However, no time-based polling techniques have been suggested that guarantee a time when polling does not occur. Moreover, previous time-based polling techniques have failed to considered hybrid coordinator (HC) or access point (AP) negotiation; that the HC/AP must act as coordinator for allocation of time on the channel. Finally, no time-based polling techniques have considered a method for making bandwidth reservations.
It would be advantageous if effective admission policies could be developed for an IEEE 802.11 network.
It would be advantageous if assigned bandwidths in an IEEE 802.11 network could be monitored and policed.